Security system with optical waveguide

Abstract

A security document comprises a substrate ( 1 ) and an optical waveguide ( 7 ). Couplers ( 10 a , 10 b ) are provided in the waveguide ( 7 ) for coupling light into and out of the waveguide. The couplers ( 10 a , 10 b ) can e.g. by gratings, scattering objects, holograms, luminescent dyes or perforations. The authenticity of the document can be verified using methods based on the properties of the waveguide.

1 . A security document comprising
 a substrate ( 1 ),   an optical waveguide ( 7 ) arranged on and/or in said substrate ( 1 ), and   at least a coupler ( 10   a ,  10   b ) for coupling light into said waveguide ( 7 ) or out from said waveguide ( 7 ).   
     
     
         2 . The security document of  claim 1 , comprising a first and a second coupler ( 10   a ,  10   b ), wherein light coupled into said waveguide ( 7 ) by means of said first coupler ( 10   a ) is at least partially transmitted to and coupled out by said second coupler ( 10   b ). 
     
     
         3 . The security document of  claim 1 , wherein said coupler ( 10   b ) comprises at least one perforation ( 14 ) extending through said waveguide ( 7 ). 
     
     
         4 . The security document of  claim 3 , wherein said coupler ( 10   b ) comprises a plurality of perforations ( 14 ) extending through said waveguide ( 7 ) and said substrate ( 1 ). 
     
     
         5 . The security document of  claim 1 , wherein said substrate ( 1 ) is non-transparent and comprises at least one transparent window or half-window ( 8   a ,  8   b ), wherein at least one coupler ( 10   a ,  10   b ) is arranged in said window or half-window ( 8   a ,  8   b ). 
     
     
         6 . The security document of  claim 5 , wherein said substrate ( 1 ) comprises at least a first and a second transparent window or half-window ( 8   a ,  8   b ), wherein a first coupler ( 10   b ) is arranged in said first window or half-window ( 8   a ) and a second coupler ( 10   b ) is arranged in said second window or half-window ( 8   b ), and wherein said waveguide ( 7 ) extends between said first and said second window or half-window ( 8   a ,  8   b ). 
     
     
         7 . The security document of  claim 1 , wherein said coupler ( 10   a ,  10   b ) comprises a grating ( 11 ). 
     
     
         8 . The security document of  claim 1 , wherein said coupler ( 10   a ,  10   b ) comprises light scattering objects embedded in or arranged on said waveguide ( 7 ). 
     
     
         9 . The security document of  claim 1 , comprising a fluorescent or luminescent dye arranged in or on said waveguide ( 7 ) for coupling light into our out from said waveguide ( 7 ). 
     
     
         10 . The security document of  claim 9 , comprising luminescent dyes of at least two different luminescent colors. 
     
     
         11 . The security document of  claim 1 , comprising a periodic microlens-array ( 15 ), and wherein said coupler ( 10   a ,  10   b ) has a periodic structure, with the microlens-array having a period substantially equal to said periodic structure. 
     
     
         12 . The security document of  claim 1 , wherein said waveguide ( 7 ) is embedded at least partially in the substrate ( 1 ). 
     
     
         13 . The security document of  claim 1 , wherein said waveguide ( 7 ) comprises at least a first layer ( 7   a ) and a second layer ( 7   b ), with said first layer ( 7   a ) having a refractive index higher than said second layer ( 7   b ), wherein said second layer ( 7   b ) is arranged between said first layer ( 7   a ) and an absorbing part of said substrate ( 1 ). 
     
     
         14 . The security document of  claim 13 , wherein said waveguide ( 7 ) further comprises a third layer ( 7   c ), with said first layer ( 7   a ) having a refractive index higher than said third layer ( 7   c ), and wherein said first layer ( 7   a ) is arranged between said second and third layers ( 7   b ,  7   c ). 
     
     
         15 . The security document of  claim 1 , further comprising a light source coupled to said waveguide ( 7 ). 
     
     
         16 . The security document of  claim 1 , wherein said waveguide ( 7 ) is a security thread embedded at least partially in said substrate ( 1 ). 
     
     
         17 . The security document of  claim 1 , wherein said waveguide ( 7 ) is a plastic foil having substantially the same size as said substrate ( 1 ).